Mocking is an essential part of unit testing, and the Mockito library makes it easy to write clean and intuitive unit tests for your Java code.
Get started with mocking and improve your application tests using our Mockito guide:
Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.
Get started with understanding multi-threaded applications with our Java Concurrency guide:
Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:
Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.
But these can also be overused and fall into some common pitfalls.
To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:
Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:
Yes, Spring Security can be complex, from the more advanced functionality within the Core to the deep OAuth support in the framework.
I built the security material as two full courses - Core and OAuth, to get practical with these more complex scenarios. We explore when and how to use each feature and code through it on the backing project.
You can explore the course here:
Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.
Get started with Spring Data JPA through the guided reference course:
Refactor Java code safely — and automatically — with OpenRewrite.
Refactoring big codebases by hand is slow, risky, and easy to put off. That’s where OpenRewrite comes in. The open-source framework for large-scale, automated code transformations helps teams modernize safely and consistently.
Each month, the creators and maintainers of OpenRewrite at Moderne run live, hands-on training sessions — one for newcomers and one for experienced users. You’ll see how recipes work, how to apply them across projects, and how to modernize code with confidence.
Join the next session, bring your questions, and learn how to automate the kind of work that usually eats your sprint time.
Regression testing is an important step in the release process, to ensure that new code doesn't break the existing functionality. As the codebase evolves, we want to run these tests frequently to help catch any issues early on.
The best way to ensure these tests run frequently on an automated basis is, of course, to include them in the CI/CD pipeline. This way, the regression tests will execute automatically whenever we commit code to the repository.
In this tutorial, we'll see how to create regression tests using Selenium, and then include them in our pipeline using GitHub Actions:, to be run on the LambdaTest cloud grid:
1. Overview
In this quick tutorial, we’re going to get familiar with a few ways to find out if a directory is empty or not.
2. Using Files.newDirectoryStream
As of Java 7, the Files.newDirectoryStream method returns a DirectoryStream<Path> to iterate over all the entries in the directory. So we can use this API to check if the given directory is empty or not:
public boolean isEmpty(Path path) throws IOException {
if (Files.isDirectory(path)) {
try (DirectoryStream<Path> directory = Files.newDirectoryStream(path)) {
return !directory.iterator().hasNext();
}
}
return false;
}For non-directory inputs, we’ll return false without even trying to load the directory entries:
Path aFile = Paths.get(getClass().getResource("/notDir.txt").toURI());
assertThat(isEmpty(aFile)).isFalse();On the other hand, if the input is a directory, we’ll try to open a DirectoryStream to that directory. Then we’ll consider the directory as empty if and only if the first hasNext() method call return false. Otherwise, it’s not empty:
Path currentDir = new File("").toPath().toAbsolutePath();
assertThat(isEmpty(currentDir)).isFalse();The DirectoryStream is a Closeable resource, so we’re wrapping it inside a try-with-resources block. As we might expect, the isEmpty method returns true for empty directories:
Path path = Files.createTempDirectory("baeldung-empty");
assertThat(isEmpty(path)).isTrue();Here we’re using the Files.createTempDirectory to create an empty and temporary directory.
3. Using Files.list
As of JDK 8, the Files.list method uses the Files.newDirectoryStream API internally to expose a Stream<Path>. Each Path is an entry inside the given parent directory. Therefore, we can also use this API for the same purpose:
public boolean isEmpty(Path path) throws IOException {
if (Files.isDirectory(path)) {
try (Stream<Path> entries = Files.list(path)) {
return !entries.findFirst().isPresent();
}
}
return false;
}Again, we’re only touching the first entry using the findFirst method. If the returned Optional is empty, then the directory is empty, too.
The Stream is backed by an I/O resource, so we’re making sure to release it appropriately using a try-with-resources block.
4. Inefficient Solutions
Both Files.list and Files.newDirectoryStream will iterate the directory entries lazily. Therefore, they will work with huge directories very efficiently. However, solutions like this will not work well in this scenario:
public boolean isEmpty(Path path) {
return path.toFile().listFiles().length == 0;
}This will eagerly load all the entries inside the directory which will be pretty inefficient when dealing with huge directories.
5. Conclusion
In this short tutorial, we got familiar with a few efficient ways to check whether a directory is empty or not.
